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Physics & Astronomy Department

Astr110 Photography Projects, Fall 2007

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Saturn Nebula (NGC 7009) , Michelle Hedg-peth

Saturn NebulaSaturn Nebula

A nebula is basically a big mass of interstellar dust and/or gas that can be seen as luminous patches, or as areas of darkness, depending on the way the mass absorbs or reflects incident radiation.   More specifically, a planetary nebula is a cloud of ionized gas that is expanding from a hot, dying star.  The reason we can see the nebula surrounding a star is because the gas in the nebula absorbs the ultraviolet radiation coming from the dying star, and reemits it as visible light through the process of fluorescence.  The Saturn Nebula was discovered on September 7, 1782 by British astronomer, Sir William Herschel.  We know today that this nebula is 3900 light-years away from Earth, about half an arc minute across, and its linear diameter is about .85 lightyears across. The nebula is in the constellation Aquarius, one of the twelve zodiac constellations. 

In the first image you can see that the outer rim of the nebula is green.
The reason we see the nebula as green is because green is the wavelength at which the light fluoresced.  This could be because there is a lot of oxygen in the atmosphere, as
oxygen produces green fluorescing.  You will notice that in the first picture there are two bright dots next to the nebula.  It is believed that this ring structure is not actually a ring, but a barrel-shaped cloud of gas that has been given off by the dying central star.  In the second picture, which only has a blue filter, we can see the star in more detail.  At the center of the image you can see that the middle of the star is more defined, and around its edges it gets a little lighter and fuzzier.  This lighter, fuzzier part is the nebula.  The star is opaque and can therefore be seen through blackbody radiation. It's easily seen in the blue because it is hot which relates to why it produces UV light.

References:

<http://www.dictionary.com>

"NGC7009, the Saturn Nebula." Red Orbit.
<http://www.redorbit.com/images/images-of-the-day/img/6858/the_saturn_nebula_ngc7009/index.html>

Plotner, Tammy. "What's Up this Week: October 1 - October 7, 2007." Universe Today.
<http://www.universetoday.com/2007/10/01/whats-up-this-week-october-1-october-7-2007/>

Bond, H. "Astronomy Picture of the Day." Hubble Heritage Team.
<http://antwrp.gsfc.nasa.gov/apod/ap010729.html>

 

Right Ascension (J2000) 21:04:12
Declination (J2000) -11:22:00
Filters used blue(B), green(V), red(R), and clear(C)
Exposure time per filter 60 seconds in C, 300 seconds in BVR
Date observed

October 23, 2007 (CBR)
October 31, 2007 (V)